Support: add reference for ARM EHABI

Add a reference to the ARM EHABI Specification as a follow up to SVN r198576

llvm-svn: 198583

llvm/include/llvm/Support/ARMEHABI.h

@@ -10,6 +10,13 @@
 // This file defines the constants for the ARM unwind opcodes and exception
 // handling table entry kinds.
 //
+// The enumerations and constants in this file reflect the ARM EHABI
+// Specification as published by ARM.
+//
+// Exception Handling ABI for the ARM Architecture r2.09 - November 30, 2012
+//
+// http://infocenter.arm.com/help/topic/com.arm.doc.ihi0038a/IHI0038A_ehabi.pdf
+//
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_SUPPORT_ARM_EHABI_H